The present application relates to air compressors, and is particularly directed to an unloader valve apparatus for an air compressor such as a vehicle air compressor used in an air braking system of a heavy vehicle like a truck.
A truck air braking system includes a vehicle air compressor which builds air pressure for the air braking system. A governor controls system air pressure between a preset maximum and minimum pressure level by monitoring the air pressure in a supply reservoir. When the supply reservoir air pressure becomes greater than that of a preset “cut-out” setting of the governor, the governor controls the compressor to stop the compressor from building air. As the supply reservoir air pressure drops to a preset “cut-in” setting of the governor, the governor returns the compressor back to building air.
The vehicle air compressor is typically a reciprocating air compressor and runs continuously. The compressor runs either in a loaded mode or an unloaded mode. When the compressor is running in the loaded mode, compressed air is delivered to the air braking system. When the compressor is running in the unloaded mode, compressed air is directed to an alternate place which is other than the air braking system. Also, when the compressor is running in the unloaded mode, an unloader valve releases pressurized air building up inside the compressor to reduce the pressurized air in the compressor, which in turn reduces the load on the device driving the compressor. This minimizes power consumption during operation of the compressor in the unloaded mode.
A drawback in known unloader valves is the difficulty in servicing the unloader valves because of the way they are installed on their respective compressors. The compressor is usually mounted in a tight location within the vehicle chassis, making it difficult to service the unloader valve without having to first remove the compressor from the vehicle chassis. Another drawback in known unloader valves is their exposure to relatively high temperatures during operation with their respective compressors. It would be desirable to provide an unloader valve which overcomes drawbacks of known unloader valves.